Method of sensitizing photographic silver halide emulsions



METHOD OF SENSITZING PHOTOGRAPHIC SILVER HALIDE EMULSIONS Original Filed June 28,` 19255 xuaau'n u .72 #und l Jop/al do www up# u u', 71 71de da Nif/6 2 ,u u w u s: s6v o fu 71 fr le n al SILVER BRGM/0f [Hl/SION JINSIYIZID WITH 2 '2 DIH! THL THldDlAZOL' PINAM THIN! C-YANINI' METHYL '10a/0l' .I6 0a was: 56 6014/'68 72'7 da Nn maa 31u10 Inu/n lmp JIM/rizzo um 2.4' amurmu rmonMzoLf, HfnAMfrH/Mr cumul: Nflllyl 4ta/u .man anni msnm uns/run um 2.

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Patented Feb. 27, 1940 UNITED STATES PATENT OFFICE METHOD OF SENSITIZING PHOTGRAPHIC SILVER HALIDE EMULSIONS Ren Stevens, Antwerp, Belgium; assigner to Gevaert Belgium Photo-Producten N. V., Antwerp,

Original application June 28, 1935, Serial No. 28,870. Divided and this application February 13, 1936, `Serial\No. 63,737.v In -Austria July 2.1,

5 Claims.

formula the thiodiazole, oxodiazole or selenodlazole ring Y Il Y I wherein X stands for sulphur, oxygen` and seleni- Various salts of heterocyclic bases have hitherto been used for the manufacture of cyanine dyes and styryl derivatives.

In comparison with the known dyes, the new lcompounds arev characterized by`a very strong sensitizing power.

1 Moreover, `they show a very high solubility not\ only in the usual organic solvents, but even in water. i l I In comparisonwwithfthe nearest -related thiazoles, they have a better resistance to acid and are produced with a much higher yield.v

These favourable `characteristics mustbe attributed to the special molecular arrangement in which the basicnature of the nitrogen atoms is neutralized bythe negative character of the symmetrically placed sulphur atom.

For carrying out the process, the base is prepared according to 'the methods described by y Stoll, Journal fr praktischeChemie (2) vol. 69,

p. 145-160. l f

The base is then condensed to an alkyl-quaternary salt,by mea-ns of an appropriate ester,for instance: dimethylsulphate, ethyliodide, methyliodide or another alkyl ester of Cl, Br, I, SO4-CH3, C104 ,or vthe like. This quaternary ammonium salt is treated in an appropriate solvent as for instance pyridine or acetic anhydride with any known condensing agents, as for instance p-dimethyl aminol benzaldehyde, an alkylester of an orthoacid, aethoxyacroleinacetal, dphenylformamidin, glutacon aldehyde dianilide hydrochloride and thev like.

The following examples illustrate the invention.

Example I 30 grams of dimethylthiodiazole lethiodide, preparedby heating together on the water bath for Y half an hour. equimolecularY vquantities of dilmetl'iylthioc'iiazole and ethyliodide, are dissolved in 200 cc. of acetic anhydride and, after addition of 50 cc. of triethyl .ortho-formic acid ester. the whole is boiled together forabout an hour.

(o1. sas- 7) The dye is precipitated by addition of ether and dissolved in alcohol, A fractional precipitation permits the separation of two dyestufls.' First rnay be isolated a blue purple dye corresponding most probably with the formula:

and which sensitizes a silver bromide emulsion nearly uniformly till about 680ML with a maximum at 590ML. 1

A further precipita-tion isolates a yellow orange dye corresponding most probably with the formula:

and which sensitizes to about 570ML with a very high maximum at about 540ml'. Either dyestui may be incorporated in a gelatino-silver bromide emulsion preferably in a concentration of about 0.05% of the silver bromide Weight.

Example II and sensitizes silver bromide gelatine emulsion with a maximum at about 550ML.

lus

Example III A mixture of 30 grams of dimethyl thiodiazole ethiodide, 50 cc. of triethyl-ortho-acetic acid ester and 250 cc. of pyridine is boiled for about three hours.

After addition of ether, the dyestui corresponding most probably With the formula:

CHI S precipitates.

Incorporated in a silver bromide gelatine emul-A sion, the dye imparts to it a strong sensitivity with a maximum at about 535ML.

I Example IV 30 grams of dimethyl thiodiazole ethiodide and 50 cc. of aethoxyacroleinacetal are dissolved in 250 cc. of pyridine and boiled for an hour.

The blue dye which can be isolated after addition of ether corresponds most probably with and sensitizes a silver bromide gelatine emulsion with a maximum at about 650ML.

Example V i A solution of 27 grams of dimethyl thiodiazole ethiodide and 50 grams of quinoline ethiodide in K 500 cc. of absolute alcohol is heated to boiling.

To the boiling solution are added 2.3 grams of sodium dissolved in about 50 cc. of anhydrous alcohol and boiling is continued for about 15 minutes.

The dye is separated by precipitation with ether and recrystallized from alcohol.

It corresponds most probably with the formula: Y

and sensitizes a silver chloride gelatine emulsion with a maximum at about 500ml.

Other symmetrical and unsymmetrical dye-V stus can be obtained for instance by means of the Acondensation product of dimethyl thiodiazole ethiodide with diphenyl formamidine of the following probable formula:y

This condensation product can easily be obtained by melting together in an oil bath at one mol. of diphenylformamidine with one mol. of dimethyl thiodiazole ethiodide. The crude prlcduct is puried by crystallization from a1- co ol.

Example VI A mixture of 25 grams of the above-named condensation product and of 20 grams of quinaldine ethiodideinl 250 cc. of pyridine is boiled for two hours. On cooling, thedye correspondingV invention, thatone or both of the CH3A groups may be exchanged for anysuitable reactive group of for instance CH2-47H3, CL S, -SH.

Moreover, the atom of sulphur in the thiodiazole ring may be exchanged for oxygen or Sele-,- nium.

'I'he substitution of oxygen for sulphur leads to dyestuifs .which have an absorptionA` spectrum and a sensitlzing action for smaller wave lengths than the-corresponding thiodiazole dyestufl's.

'Ihe substitution of selenium for sulphur leads to dyestufls which have an absorption spectrum and a sensitizing action fr longer wave lengths than the corresponding thiodiazole dyestuffs.

It is to be understood that the invention is not -limited to the'foregoing examples or to the specie details given therein. y

The drawing axed to this specilcationand forming part thereof shows sensitizing curves;

In the drawing;

Fig. l is the sensitizing curve of a nonlsensitized silver bromide emulsion as usually employed for photographicv materials, while Figs.v 2 to 6 show corresponding curves of an Other alkyl'de'rivatives, more par- Y emulsion of the same kind when sensitizied by an addition of the YYdyestli's described inv theY above Examples 1 'and 3 to 6, respectively.l

The dye may be added to the emulsion in the form of a solution. It may be incorporated in the emulsion during 'any stage of its production or the finished emulsion layer may be bathed in a solution of the dye.

I claim: l

1. As a photographic material, a silver halide emulsion with an addition of a dyestuff of the general formula An wherein R is Ia member of the group constituted by methyl and ethyl, while Y and Y are alkyls, An is anr anion, X is a memberof the group constituted bysulphur, oxygen and selenium Vand Z represents the non-metallic 'atoms necessary l to complete a heterocyclic nucleus selected from the group consisting of veand six-membered heterocyclic nuclei; n being zero or an integer.

2. As a photographic material, a silver halide emulsion with an addition of a dyestui as defined in claim 1, wherein the nucleus, which' is completed by the atoms represented by Z, forms part of a condensed system of nuclei.

3. As apliotographic material, a silver halide emulsion with an addition ofk a dyestuff as dened in claim 1, wherein the H of the middle carbon atom of the polymethenyl chain is substituted by an alkyl group. A

4. As a photographie material, the silver halide emulsion with an addition of a dyestuiT as defined in Claim 1, wherein the H of the middle carbon atom of the polymethenyl chain is substituted by the radical whue n=1, sra-Y and is 5. As a photographic material a silver halide emulsion withan addition of a dyestuff of the formula 1 l /Hal -N-N f l n; -CH=c15I-CH=C C-R x l v x wherein R is a. member of the group constituted by methyl and ethyl, while Hal is halogen, Y is an alkyl and X is a member of the group constituted by sulphur, oxygen and selenium.

REN STEVENS. 

